RTAI, RTLinux and fully preemptive patch

El 22/11/2010 13:28, softwareEngineer escribió:


That's Linux on top of a specific real-time kernel.

Look for Xenomai too.



That's Linux on top of another specific real-time kernel, nowadays
submerged in a windy river.



That's Linux with patches in its kernel.



No, those are two approaches (one: make Linux run as a task on top of an
RTOS, use directly the RTOS when you need hard RT, but Linux apps when
you don't; two: fix Linux kernel to make it more preemptable and less
unpredictable, use always Linux applications) to solve the same problem.
Each approach with its variations, trade marks and the like.



Not me... yet.

RT preempt: The advantage is you can use generic POSIX (with exceptions) to
program your hard realtime application and you can do it in userland.
Successfully used in various industrial projects.
(https://www.osadl.org/Realtime-Linux.projects-realtime-linux.0.html )

jbe

If you need hard realtime you need to stick with RTL or RTAI. Both
have a HAL beneath the linux jernel that provide hard-realtime API.
If soft-RT is good enough for you the standard 2.6 kernel preforms
pretty well as long as don't hit a shitty driver ported from early 2.4
kernel versions.
In 2.6 99% of the kernel code is preemtible (only the first level ISRs
are not but those are well written in most cases)

I've used soft RT on 2.6 (and the latest 2.4) kernels without
significant problems.